Electronic equipment in the telecommunications and other industries is generally designed based upon a modular format. The modular subassemblies that combine to make up an electronic assembly are generally housed in a chassis that has multiple racks with modular compartments.
The modular design provides several advantages including reliability, ease of maintenance and economic savings. For example, if a module in the electronic assembly malfunctions, a service technician can remove and replace the malfunctioning module without taking the system employing the module out of service. If necessary, the malfunctioning module can then be repaired at a service location by specialized technicians familiar with that type of module. This permits field maintenance to be carried out by less skilled personnel and also results in a more reliable system.
The type of chassis used to accommodate the modules varies depending on the environment where the equipment is located. One type of chassis commonly used in the telecommunications business has a series of modules installed adjacent to one another. This type of chassis is commonly employed, for example, to house rectifier modules that combine to make up a rectifier assembly.
Regardless of the type of electronic equipment the chassis assembly accommodates, the chassis is used to provide the framework to deliver electrical power to or from the modules and provide for electrical connectivity between modules. Because of the type of electrical components that have to be used in rectifiers or converters, power supply modules are generally of the type that will generate electromagnetic emissions that can cause interference with other nearby electronic devices. For this reason, the various regulatory agencies will generally specify a maximum level of EMI emission that a power system is permitted to radiate. Because of this, one of the major concerns of manufacturers and users of telecommunications power systems is the level of EMI emission of such a system.
One method of controlling radiated EMI emissions in a modular electronic assembly is the establishment of low impedance connections to provide a common voltage potential between a chassis and the various modules housed in the chassis. By providing a common ground voltage potential, the radiated EMI generated by differing voltages is reduced.
One prior art method of providing a common grounding voltage between each conductive case in a chassis is to couple each module to the chassis with a separate wire. This approach, however, exhibits characteristic impedances that are too high to be effective for efficient EMI control. Another conventional method employs a conductive, compliant gasketing material. However the use of gasketing materials adds to both materials and labor costs and are therefore undesirable. Another EMI control method is to provide for a direct contact between the chassis and the module cases and between cases of adjacent modules. However, even in situations where a common voltage potential can be established between module cases and the chassis or between adjacent module cases by direct contact, the degree of design tolerance necessary to provide for a direct connection common path for the modular case to the chassis or between adjacent module cases generally increases the total manufacturing cost and decreases reliability.
Accordingly, what is needed in the art is a device that is employable in an electronic equipment chassis that can establish a common voltage potential between the electronic modules and the chassis housing the modules to provide an assured grounding connection that reduces EMI emissions to an acceptable level.